In malignant human gliomas, the tyrosine kinase receptor c-Met and its ligand hepatocyte growth factor (HGF) are frequently overexpressed and the tumor suppressor PTEN is frequently mutated. In the previous grant, we uncovered multiple mechanistic and functional interactions between PTEN and c-Met pathway and found that c-Met activation and PTEN loss have additive effects on glioma malignancy. In this competitive renewal, we propose a continuation of the analysis of PTEN/c-Met in gliomas with a focus on novel mechanistic interactions between PTEN and c-Met pathway and on testing new preclinical therapeutic agents and strategies. In aim #1, we will study the regulation of PTEN phosphorylation and half-life by HGF that we recently discovered. The findings will uncover a new mechanism of HGF-induced malignancy and of PTEN post-translational regulation. In aim #2, we will test the hypothesis that PTEN downregulates c-Met expression via a new pathway involving p53 and microRNA-34a. The findings could explain the concurrent PTEN loss and c-Met overexpression in glioblastoma and uncover a new mechanism of c-Met expression regulation. In aim #3, we will determine the effects of PTEN expression on the in vivo therapeutic efficiency of anti-HGF monoclonal antibodies and a new orally bioavailable small molecule inhibitor of c-Met. We will also assess the therapeutic value of combining anti-HGF or anti-c-Met therapies with mTOR inhibitors that counteract the effects of PTEN loss in PTEN- mutated xenografts. The translational experiments will be performed using primary glioma cell-derived and glioma stem cell-derived xenografts. Successful completion of the proposed experiments will provide new mechanistic insights into the regulation of PTEN and c-Met and uncover previously unknown molecular interactions between them. The findings will also provide necessary and timely information for the use in a clinical setting of clinically applicable anti-HGF and anti-c-Met therapies also in combination with mTOR inhibitors. The use of clinically applicable agents in primary and glioma stem cell animal models will confer high validity and preclinical significance to the obtained results. PUBLIC HEALTH RELEVANCE: We previously found that increase of the oncogene c-Met and loss of the tumor suppressor PTEN have additive effects on the growth of glioma brain tumors. We propose to study new mechanisms with which c-Met and PTEN regulate each other in gliomas. We also propose to test the effects of PTEN on new clinically useful drugs that target c-Met and also test new drugs and drug combinations for glioma therapies. The results will lead to the development of new glioma therapeutic strategies and provide important information for the use of the new drugs in the clinic.